History of Petroleum:

Petroleum, or crude oil as it is often called, is a naturally occurring flammable liquid. The name petroleum was first used by the German mineralogist Georg Bauer in 1546. Some natural gas may be found dissolved in petroleum some of which is recovered or burnt during oil extraction. These are found naturally below the surface of the Earth in many places. It is extracted by drilling in places where the oil reserves are found or expected.
Crude oil consists of a complex mixture of hydrocarbons and other organic compounds. These are separated easily in a refinery into large number of consumer products like gasoline or petrol, kerosene, asphalt and chemical reagents used in plastics and pharmaceuticals. 
Petroleum, in one form or another, has been used since ancient times.  Apparently asphalt was used in the construction of walls and towers of Babylon more than 4000 years ago using oil pits located nearby. Ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society. Petroleum was also extensively used by the some Native American tribes for religious rituals as also for medicinal purposes to cure aching joints. Later farmers who knew about oil in the early 1800s saw crude oil seeping on the agricultural fields as a nuisance to agriculture and water supplies. The importance of petroleum in recent times is due mostly to the invention of the internal combustion engine used in automobiles and industry.
Drilling of the world's first oil well is credited with Edwin Drake in 1859 at Titusville, Pennsylvania in the USA, though there were also attempts in Poland, Germany and Canada at around the same time. However the method developed by Drake, of using a pipe up to the bedrock below to drill from inside the pipe, were used extensively by other oil drillers.
Around the same time in the 1860s oil exploration activities began in the dense jungles of Assam in India. The earliest recorded reference to oil in Assam is traced to Lieut. Wilcox who saw the oil on the surface at Supkhong "bubling to the surface". In March 1867 oil was struck in a well near Makum which was the first such effort in Asia. The first commercial discovery of crude oil (in India as well as Asia) was made in 1889 at Digboi in Brahmaputra valley of Assam. Apart from the people involved in drilling, the only other inhabitants of the region were the elephants, rhinos, snakes and of course leeches.
Legend has it that an elephant employed by the Assam Railway and Trading Company (AR&T Co) returned one day with large traces of oil on its feet.  Intrigued by the unusual smell and texture of the black liquid, the owners of the elephant tracked its foot prints to the source and found seepage of oil to the surface. The Englishman at the helm then cried "Dig Boy! Dig". Hence the name "Digboi"-- a tiny hamlet hidden in the lush green rolling hills of Assam. This legend has grown over time  and there are also many versions which cannot be corroborated, but 
it makes an interesting reading nevertheless.
The Assam Oil Company was founded in 1899 to commercially extract oil from Digboi oil fields. Digboi still has the distinction of being the world's oldest continuously producing oil field.